v3.1 Qt2

This is the second snapshot of the upstream pull request.

Fedora packages from Copr:

• Fedora 40: solvespace-qt-3.1-1.fc40.x86_64.rpm
• Fedora 41: solvespace-qt-3.1-1.fc41.x86_64.rpm

v3.1 Qt

This is a snapshot of the upstream pull request.